Convergent Perturbation Theory for the lattice $\phi^4$-model

Abstract

The standard lattice perturbation theory leads to the asymptotic series because of the incorrect interchange of the summation and integration. However, changing the initial approximation of the perturbation theory, one can generate the convergent series. We study the lattice $\phi^4$-model and compare the operator $\langle\phi_n^2\rangle$ calculated using the convergent series and obtained by Monte Carlo simulations.